Eyepiece lens systems that form magnified virtual images of objects have been widely used in various optical devices, such as loupes, microscopes, and the like.
In specific, an image of a region on an object to be observed is formed on the end at the object (hereinafter, object end) of an image transmitter composed of an optical fiber bundle of an endoscope, the image is transmitted to the end at the eyepiece lens (hereinafter, eyepiece end) of the optical fiber bundle, and the transmitted image is enlarged through the eyepiece lens system into a magnified virtual image of the object to be observed.
Alternatively, video content, for example, associated with virtual reality, movies, or games has been two-dimensionally displayed on a small image display device, such as a liquid-crystal display device, an EL display device, or any other device, in recent years; the two-dimensional image has been enlarged through an eyepiece lens system into a magnified virtual image of an object to be observed.
Eyepiece lens systems, the observer often wears on his/her head or face, should preferably be lightweight and compact.
An eyepiece lens system is also known that includes only four lenses and is lightweight and compact.
Known eyepiece lens systems have low telecentricity on the object side.
If the telecentricity is low on the object side, the observation through an eyepiece lens system of a two-dimensional image appearing on a liquid-crystal display device, an organic EL display device, or any other device or an image of an observed region formed on the object end of an optical fiber bundle of an endoscope may vary in brightness and color depending on the angle of view. This phenomenon precludes the acquisition of satisfactory high-resolution observed images.
Magnified virtual images observed through endoscopes or observed as video content associated with movies and games are required to have high resolution, while eyepiece lens systems are required to satisfactorily correct aberration.